[c#] izbris vsebin v vseh gradnikih

private void button1_Click(object sender, EventArgs e)
{
  IEnumerable<Control> controlList = GetControls(this);

    foreach (Control c in controlList)
      c.Text = "";
}

public static IEnumerable<Control> GetControls(Control form)
{
     //Sprehodimo se skozi controle
     foreach (Control childControl in form.Controls)
     {   //Če ima controla otroke, potem se prehodimo še skozi otroke
         foreach (Control grandChild in GetControls(childControl))
         {
            yield return grandChild;
         }
           //vrnemo še kontrolo
           yield return childControl;
      }
}

EDIT: bolj šolski primer

private void button1_Click(object sender, EventArgs e)
        {
            List<Control> controlList = GetControls(this);

            foreach (Control c in controlList)
                c.Text = "";
        }

        public static List<Control> GetControls(Control form)
        {
            List<Control> controlList = new List<Control>();
            //Sprehodimo se skozi controle
            foreach (Control childControl in form.Controls)
            {   //Če ima controla otroke, potem se prehodimo še skozi otroke
                foreach (Control grandChild in GetControls(childControl))
                {
                    controlList.Add(grandChild);
                }
                //vrnemo še kontrolo
                controlList.Add(childControl);
            }

            return controlList;
        }